US President George Bush is tonight beginning his historic and controversial state visit to Britain amid unprecedented security.

After touching down at Heathrow Airport, Mr Bush and his wife Laura were flown to Buckingham Palace by the presidential helicopter, Marine One, to a private welcome by Queen Elizabeth and the Duke of Edinburgh.

At the airport the presidential party were greeted by the Prince of Wales.

It is the first such visit by a US President since Woodrow Wilson in 1918.

An opinion poll published today suggests that the majority of people in Britain support Mr Bush's state visit.

The ICM survey for The Guardian suggests 43% of British people are in favour, while 36% oppose it.

Downing Street has been urging those who support the visit to make their voices heard during Mr Bush's four-day visit.

His trip coincides with a new poll in the US suggesting that his popularity is at an all-time low among US voters, just a year before the next presidential elections.

The British prime minister, Tony Blair, has defended the decision to invite Mr Bush at this time, despite increasing public disquiet and political criticism.

However, London's mayor, Ken Livingstone, has sent a message of support to protesters, telling them they have the moral high ground and that the world will be watching them as they protest against what he described as an illegal war and occupation in Iraq.

Protests planned in London

In London, campaigners are finalising plans for a series of demonstrations against the visit, beginning this evening.

The Stop The War Coalition is predicting that more than 100,000 people will join the biggest demonstration in central London on Thursday.

More than 14,000 police officers will be on duty during the controversial visit, at a cost of £5m.

Despite the high level of security, protesters have been given permission to march down Whitehall on Thursday, close to the Houses of Parliament at Westminster.

Iraq to dominate agenda

With military losses escalating, Iraq is expected to dominate talks at Downing Street between Mr Blair and Mr Bush.

But the leaders will also discuss trade, the Middle East, climate change and AIDS.

On Friday, the two leaders will visit Mr Blair's Sedgefield constituency in Durham in the north of England, before Mr Bush returns to the US.